EMBO: A team of European researchers has devised a strategy to ensure that
adult epidermal stem cells are safe before they are used as treatments
for patients. The approach involves a clonal strategy where stem cells
are collected and cultivated, genetically modified and single cells
isolated before being rigorously tested to make sure they meet the
highest possible safety criteria. The strategy, which is published
online in EMBO Molecular Medicine, is inspired by the
approaches the biotechnology industry and regulatory affairs authorities
have adopted for medicinal proteins produced from genetically
engineered mammalian cells.
“Until now there has not been a systematic way to ensure that adult
epidermal stem cells meet all the necessary requirements for safety
before use as treatments for disease,” says EMBO Member Yann Barrandon,
Professor at Lausanne University Hospital, the Swiss Federal Institute
of Technology in Lausanne and the lead author of the study. “We have
devised a single cell strategy that is sufficiently scalable to assess
the viability and safety of adult epidermal stem cells using an array of
cell and molecular assays before the cells are used directly for the
treatment of patients. We have used this strategy in a proof-of-concept
study that involves treatment of a patient suffering from recessive
dystrophic epidermolysis bullosa, a hereditary condition defined by the
absence of type VII collagen which leads to severe blistering of the
skin.”
The researchers cultivated epidermal cells from the patient that can
be used to regenerate skin. The scientists used their array of tests to
determine which of the transduced cells met the necessary requirements
for stemness – the characteristics of a stem cell that distinguish it
from a regular cells – and safety. Clonal analysis revealed that the
transduced stem cells varied in their ability to produce functional type
VII collagen. When the most viable, modified stem cells were selected,
transplantation onto immunodeficient mice regenerated skin that did not
blister in the mouse model system for recessive dystrophic epidermolysis
bullosa and produced functional type VII collagen. Safety was assessed
by determining the sites of integration of the viral vector, looking for
rearrangements and hit genes, as well as whole genome sequencing.
“Our work shows that at least for adult epidermal stem cells it is
possible to use a clonal strategy to deliver a level of safety that
cannot be obtained by other gene therapy approaches. A clonal strategy
should make it possible to integrate some of the more recent
technologies for targeted genome editing that offer more precise ways to
change genes in ways that may further benefit the treatment of disease.
Further work is in progress in this direction.”
A single epidermal stem cell strategy for safe ex vivo gene therapy
Stéphanie Droz-Georget Lathion, Ariane Rochat, Graham Knott,
Alessandra Recchia, Danielle Martinet, Sara Benmohammed, Nicolas
Grasset, Andrea Zaffalon, Nathalie Besuchet Schmutz, Emmanuelle
Savioz-Dayer, Jacques S. Beckmann, Jacques Rougemont, Fulvio Mavilio and
Yann Barrandon
Read the paper: